The present invention is directed to a method of bypassing the electric current of at least one of a plurality of electrolytic cells which are connected in series to an electrolytic power source thus forming an electrolytic apparatus.
In an electrolytic apparatus utilizing an ion exchange membrane method or a diaphragm means for subjecting alkali metal halogenide aqueous solution or the like to electrolysis, a plurality of electrolytic cells are connected in series to an electrolytic power source. When it is desirable to repair or replace one of the electrolytic cells in such an electrolytic apparatus, it is necessary to bypass the electric current of the electrolytic cell while the remaining electrolytic calles are still operated with the rated current.
Previously, the connecting terminals of a short-circuit unit were connected to the anode and cathode terminals provided on the outer surface of the electrolytic cell, respectively, to form a bypass circuit for the electrolytic current. When the switch of the short-circuit unit was closed, the electrolytic current would flow through the short-circuit unit thereby bypassing, the current passing through the electrolytic cell. The electrolyte in the electrolytic cell can then be drained or the entire electrolytic cell removed from the electrolytic apparatus.
However, in carrying out the above-mentioned conventional method of bypassing the electric current of an electrolytic cell, when the switch of the short-circuiting unit is closed a large reverse current flows in the electrolytic cell. Although the reverse current decreases abruptly, a small reverse current will continue to flow in the electrolytic cell for a long period of time before finally approaching zero.
In the electrolysis of an alkali metal halogenide solution, a cathode is utilized which is provided for forming an active coating layer such as a porous nickel coating layer low in hydrogen overvoltage on an electrically conductive base of soft steel or the like. In has been found that the reverse current dissolves the electrically conductive base and the active coating layer of the cathode and if the reverse current flows for a long period of time, the cathode will be adversely affected thereby.